TRANSACTIONS OP THK SECTIONS. 211 



In accordance with his directions, a stont bar about 5 feet long was armed at the 

 tail-end with two expansive cup-shaped and cup-leathered pistons, placed with such 

 an interval between them, as to ensure the mamtcnance of pressure while passing- 

 stop-valves and branches. Its front end was armed with four pairs of scrapers, 

 each formed of Hat iron bar, bent tlatways like the letter U reversed, the cross 

 sti-okes forming cutting edges which the spring of the metal pressed against the 

 sides of the pipe, the whole circumference of which they together embraced, and 

 intended to act not imlike the patent road-scraper. The cutting edges were 

 " skewed" so as to prevent their dropping into, and laying hold of any pipe-joints 

 more than usually open; a regulated flow of water was permitted to pass the 

 piston, so as to drive the scrapings forward. 



The Torquay Local Board, on whom the responsibility rested, were induced, on 

 ]\Ir. Fronde's strong recommendation, to allow the implement to be tried on a mile 

 of main ; not without hesitation, for the shortness of the existing water-supply en- 

 hanced the anxiety attending so novel and bold an experiment, which, should the 

 scraper stick fast, might involve serious delay in the reinstatement of the delivery ; 

 the main had to be cut and closed again in two places, at all events. The 

 scraper, happilj', travelled the mile without difficulty ; and the pressure-gauge test, 

 tried before the operation, and again after the flow had been reinstated, showed, 

 by the consequent reduction of pressm'e at the upper end of the distance, and its 

 increase at the lower end, that the scraped pipe drew away the water from above, 

 and delivered it belowVith greatlj' increased freedom : 21 feet of "head " had pre- 

 viously been consumed on the distance, 7 feet only were consumed on it subse- 

 quently, — a dirterence promising an improvement of 75 per cent, in the delivery, 

 when the pipe shoidd be scraped throughout*. 



One material cause of anxiety was removed, by finding that the grating noise 

 made by the scraper in transitu indicated its exact pof<ition to all observers who 

 accompanied it. Thus encouraged, the Local Board entrusted to Mr. Froude the 

 completion of the work throughout ; but the experience gained in the trial showed 

 that an amended scraper and complete appliances would be required for it. 



Lengths of pipe, fitted with moveable covers to admit of the insertion of the 

 scraper, were interpolated at suitable positions ; and a new scraper was made fitted 

 with hard steel cutters, pressed against the pipe by independent steel springs, — im- 

 provements which the preliminary trial had shown to be essential to a persistent 

 and vigorous scraping action. In the extended operation, serious difficulties which 

 fortunately had not appeared in the preliminary trial, were encountered in the 

 large number of stones (some several inches in diameter) which had been carelessly 

 enclosed in the pipe when laid ; and it became necessary to clear the way for the 

 scraper by passing first a strong cast-u-on cup, which commmuted the smaller 

 stones and picked up the large ones, and eventually the whole work was completed. 

 For reasons too long to state here, the impi-ovemeut first attained was only 40, 

 not 70 per cent., as had been hoped ; but subsequent repeated scrapings with a very 

 improved pattern of scraper, wliich does not, however, admit of brief description, 

 have increased the delivery by considerably over 100 per cent.; it was only .317 

 gallons per minute bef(n'e opei-ations were commenced, it was G55 after the most 

 recent scraping; and the operation is now so simplified and well understood, that 

 but for the change of diameter, which involves a change of scraper, the whole 

 length of main could be traversed witliout any pause. 



It is found that very soon after the scraping a perceptible decline of delivery 

 takes place, proljably owing to a gradual erosion of the smeared smoothness, which 

 is likelv to be an immediate result of the operation ; and besides, minute pustules 

 of oxide begin at once to form, and it is evident that mere infinitesimal roughness 

 sensibly obstructs the flow, but in its practical aspect the operation is perfectly 

 successful. 



On some Blffuultles in the received View of Fluid Friction. 

 By William Fkoitde. 

 The very great variations in frictloual resistance exhibited by the flow of water 



* Mr. Appold died the day before this first successful trial of his suggestion. 



14* 



